Orientation detection device and non-transitory computer readable medium

ABSTRACT

An orientation detection device obtains a detection information of a sensor that detects a displacement in the vertical direction occurring in the vehicle, computes a pitch angle of the vehicle on the basis of the detection information, obtains a gradient information indicating a gradient of a road on which the vehicle travels, and corrects a correlation between the detection information used in computation and the pitch angle on the basis of the gradient information.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of InternationalPatent Application No. PCT/JP2018/035277 filed on Sep. 25, 2018, whichdesignated the U.S. and claims the benefit of priority from JapanesePatent Application No. 2017-217469 filed on Nov. 10, 2017. The entiredisclosures of all of the above applications are incorporated herein byreference.

TECHNICAL FIELD

The present disclosure relates to an orientation detection device and anon-transitory computer readable medium for detecting orientation of avehicle.

BACKGROUND

As an example of a device for detecting orientation of a vehicle, aself-position calculation device has a projector projecting a patternlight onto the surface of a road around a vehicle and an imaging unittaking an image of the road surface in an area in which the patternlight is projected. The self-position calculation device calculates theorientation angle of the vehicle on the basis of position of the patternlight on the road surface.

SUMMARY

The present disclosure describes an orientation detection device fordetecting orientation of a vehicle, and a non-transitory computerreadable medium therefor. The orientation detection device obtains adetection information of a sensor, which detects a displacement in thevertical direction occurring in the vehicle, computes a pitch angle ofthe vehicle on the basis of the detection information, obtains agradient information indicating a gradient of a road on which thevehicle travels, and corrects a correlation between the detectioninformation used in computation and the pitch angle on the basis of thegradient information.

BRIEF DESCRIPTION OF DRAWINGS

Features and advantages of the present disclosure will become moreapparent from the following detailed description made with reference tothe accompanying drawings.

FIG. 1 is a block diagram illustrating an overall image of an in-vehiclesystem including a display control device according to a firstembodiment of the present disclosure.

FIG. 2 is a perspective view illustrating an example of a vehicle heightsensor.

FIG. 3 is a diagram illustrating a state of a vehicle on a flat roadhaving no gradient.

FIG. 4 is a diagram illustrating the state of a vehicle on a slopingroad and the relation between a road gradient and a vehicle gradient.

FIG. 5 is a diagram illustrating an example of AR display visuallyrecognized by the driver on a flat road.

FIG. 6 is a diagram illustrating an example of AR display visuallyrecognized by the driver on a sloping road.

FIG. 7 is a diagram illustrating an example of a method of calculating aroad gradient from three-dimensional map data.

FIG. 8 is a diagram illustrating a tilt model calculating a pitch anglefrom an output value of a vehicle height sensor and illustrating anexample of a correlation function corrected on the basis of roadgradients.

FIG. 9 is a flowchart illustrating an orientation detecting processexecuted by an orientation computation unit.

FIG. 10 is a flowchart illustrating a correction value computing processexecuted by a correction value computation unit.

FIG. 11 is a block diagram illustrating a whole image of an in-vehiclesystem including a display control device according to a secondembodiment.

FIG. 12 is a diagram for explaining a method of calculating a roadgradient by using a front camera.

FIG. 13 is a diagram for explaining the details of a process ofcalculating a road gradient from an image shot in a scene illustrated inFIG. 12.

FIG. 14 is a block diagram illustrating a whole image of an in-vehiclesystem including a display control device according to a thirdembodiment.

FIG. 15 is a block diagram illustrating a whole image of an in-vehiclesystem including a display control device according to a fourthembodiment.

FIG. 16 is a block diagram illustrating a whole image of an in-vehiclesystem including a display control device according to a fifthembodiment.

DETAILED DESCRIPTION

As an example of a device for detecting orientation of a vehicle, it hasbeen proposed a self-position calculation device having a projectorprojecting a pattern light onto the surface of a road around a vehicleand an imaging unit taking an image of the road surface in an area inwhich the pattern light is projected. The self-position calculationdevice calculates the orientation angle of the vehicle on the basis ofposition of the pattern light on the road surface.

However, having the projector for projecting a pattern light fordetecting the orientation angle of a vehicle results in complication ofthe configuration. Therefore, it is conceivable to employ aconfiguration of computing the orientation angle of a vehicle on thebasis of detection information of a sensor, such as an accelerationsensor or a vehicle height sensor, which is generally mounted in avehicle for detecting a displacement in the vertical direction. However,in the case of using such a sensor, it is newly found that,particularly, computation of a pitch angle is easily influenced by thegradient of a road on which the vehicle is traveling and decrease indetection precision is caused.

The present disclosure provides an orientation detection device capableof suppressing decrease in detection precision of a pitch angle causedby a road gradient while avoiding complication of a configuration usedfor orientation detection.

According to an aspect of the present disclosure, an orientationdetection device for detecting orientation of a vehicle includes: adetection information obtaining unit obtaining a detection informationof a sensor that senses a displacement in the vertical directionoccurring in the vehicle; an orientation computation unit computing apitch angle of the vehicle on the basis of the detection information; agradient information obtaining unit obtaining a gradient informationindicating a gradient of a road on which the vehicle travels; and acorrelation correction unit correcting a correlation between thedetection information used in computation of the orientation computationunit and the pitch angle on the basis of the gradient information.

The present disclosure also provides a non-transitory computer readablemedium storing a computer program product comprising instructions fordetecting an orientation of a vehicle. According to an aspect, theinstructions being configured to, when executed by a processor, causethe processor to: obtain a detection information of a sensor that sensesa displacement in the vertical direction occurring in the vehicle;compute a pitch angle of the vehicle on the basis of the detectioninformation; obtains a gradient information indicating a gradient of aroad on which the vehicle travels; and correct a correlation between thedetection information used in computation and the pitch angle on thebasis of the gradient information.

In the orientation detection device and the non-transitory computerreadable medium according to the above aspects, the correlation betweendetection information of the sensor and the pitch angle as describedabove can indicate a substantially unique change in accordance with themagnitude of a road gradient. By paying attention to such a phenomenon,in the above-described aspects, the correlation between the detectioninformation of the sensor and the pitch angle is corrected to a stateadapted to the road gradient of the road on which the vehicle istravelling. By the above, also during travel on a road with a gradient,the pitch angle computed becomes insusceptible to the influence of theroad gradient and can become a value maintaining precision. Therefore,while avoiding complication of the configuration for orientationdetection, decrease in detection precision of a pitch angle caused by aroad gradient can be suppressed.

Embodiments of the present disclosure will be hereinafter described withreference to the drawings.

First Embodiment

A display control device 100 according to a first embodiment of thepresent disclosure illustrated in FIG. 1 is applied to a virtual imagedisplay system 110 used in a vehicle. The virtual image display system110 presents various information related to a vehicle to the driver byusing a virtual image Vi superimposed on the foreground of the vehicle.The virtual image display system 110 is configured by combining anoptical unit 10, the display control device 100, and the like.

The optical unit 10 is one of a plurality of displays mounted in thevehicle and electrically connected to the display control device 100.The optical unit 10 projects light of a display light image in aprojection area PA designated in a windshield WS of the vehicle anddisplays the virtual image Vi of the display light image so that it canbe visually recognized by an occupant (for example, the driver) of thevehicle. The optical unit 10 has a projector 11 and a reflective opticalsystem 12 as components for displaying the virtual image Vi.

The projector 11 projects light of a display light image formed as thevirtual image Vi toward the reflective optical system 12. The reflectiveoptical system 12 projects the light of the display light image incidentfrom the projector 11 to the projection area PA. The light projected tothe windshield WS is reflected by the projection area PA toward an eyepoint side and perceived by the driver. Alternatively, the projectionarea PA may be designated in a projection member such as a combinerprovided separately from the windshield WS.

The display control device 100 is an electronic control unit controllingdisplay by the display mounted in the vehicle. The display controldevice 100 has a function of detecting the orientation of the vehicle asone of functions for controlling virtual image display by the opticalunit 10. The display control device 100 controls so as to correct theprojection position and the projection shape of a display light image inaccordance with an orientation change of the vehicle and form thevirtual image Vi of a proper shape in a proper position in theforeground (refer to FIG. 6). The display control device 100 iselectrically connected directly or indirectly to a self-vehicle positiondetection device 21, a three-dimensional map database 22, a modelstorage unit 24, a vehicle state sensor 26, an occupant sensor 27, avehicle height sensor 40, and the like to obtain information necessaryto detect the vehicle orientation.

The self-vehicle position detection device 21 receives positioningsignals from a plurality of satellites. The self-vehicle positiondetection device 21 can receive positioning signals from positioningsatellites of at least one satellite positioning system from satellitepositioning systems such as GPS, GLONASS, Galileo, IRNSS, QZSS, andBeidou. The self-vehicle position detection device 21 measures theposition of the self-vehicle, on which the display control device 100 ismounted, on the basis of the received positioning signals. Theself-vehicle position detection device 21 sequentially outputs themeasured vehicle position information toward the display control device100.

The three-dimensional map database (hereinbelow, “three-dimensional mapDB”) 22 is configured mainly by a large-capacity storage medium storinga number of pieces of three-dimensional map data and two-dimensional mapdata. The three-dimensional map data is high-precision map data whichenables automatic driving of a vehicle. In the three-dimensional mapdata, a landform and a structure are expressed by a point group havingthree-dimensional coordinate information. The three-dimensional map DB22 can update three-dimensional map data to latest information through anetwork. The three-dimensional map DB 22 can provide three-dimensionalmap data around and in the travel direction of a vehicle to the displaycontrol device 100 in accordance with a request from the display controldevice 100. In the case where three-dimensional map data in an arearequested to be provided is not ready, the three-dimensional map DB 22provides usual two-dimensional map data used for navigation or the liketo the display control device 100.

The model storage unit 24 is configured mainly by a storage medium andstores a tilt model necessary to compute a tilt of the vehicle withrespect to the road surface. A tilt model is a unique numerical value,function, or the like which varies among vehicles and is obtained inadvance by examination, calculation, or the like. The model storage unit24 stores a function (refer to FIG. 8) indicating a correlation betweenan output value of the vehicle height sensor 40 and a pitch angle of thevehicle as one of tilt models. The model storage unit 24 provides a tiltmodel corresponding to the present state of the vehicle to the displaycontrol device 100 in response to a request from the display controldevice 100.

The vehicle state sensor 26 is a sensor group mounted in the vehicle anddetecting the state of the vehicle. The vehicle state sensor 26includes, for example, a vehicle speed sensor, a steering angle sensor,an acceleration sensor, an accelerator position sensor (hereinbelow, “APsensor”), and a brake pedal sensor. To the display control device 100,vehicle speed information detected by the vehicle speed sensor, steeringangle (handle angle) information detected by the steering angle sensor,acceleration information in the front-back direction detected by theacceleration sensor, and the like is sequentially provided. In addition,to the display control device 100, accelerator position informationdetected by the AP sensor, brake pedal force information detected by thebrake pedal sensor, and the like is also sequentially provided.

The occupant sensor 27 is a sensor for measuring the number of occupantsin the vehicle. The occupant sensor 27 is disposed in each of theseating faces of the driver's seat, the front passenger seat, and therear passenger seats. The occupant sensor 27 is, for example, a switchwhich is turned on/off by application of a load and detects seating ofan occupant on each of the seating faces. A detection result by theoccupant sensor 27 is information indicating a seat on which an occupantsits in the vehicle and is sequentially obtained by the display controldevice 100.

The vehicle height sensor 40 illustrated in FIG. 2 is a sensor detectinga displacement in the vertical directions which occurs in the vehicle tomeasure the height of the body from the road surface on which thevehicle stands. The vehicle height sensor 40 measures a sinking amountwith respect to the body, of a specific wheel which displaces in thevertical direction by the operation of a suspension arm suspended by thebody. Concretely, the vehicle height sensor 40 obtains a relativedistance between the body and the suspension arm as detectioninformation and sequentially outputs it toward the display controldevice 100. Only one vehicle height sensor 40 is attached in a placerearward from the center in the front-rear direction of the vehicle andmeasures a displacement in the vertical directions in the rear part ofthe vehicle. In the case of a right-hand-drive vehicle, the vehicleheight sensor 40 is attached to the left-rear suspension. In the case ofa left-hand-drive vehicle, the vehicle height sensor 40 is attached tothe right-rear suspension. The vertical direction is the verticaldirection which is along the direction of gravity.

The vehicle height sensor 40 has a first coupling part 41, a secondcoupling part 42, and a measuring unit 43. The first coupling part 41can turn relative to the second coupling part 42. The first couplingpart 41 is coupled to one of the body and the suspension arm (forexample, the body). As an example, the first coupling part 41 isattached to a sub frame SF of the body.

The second coupling part 42 is coupled to the other of the body and thesuspension arm which is not coupled to the first coupling part 41 (forexample, the suspension). The second coupling part 42 is attached to,for example, a lower arm LA of a plurality of supporting elementssupporting the wheel in a suspension device.

The measuring unit 43 measures a displacement amount in the verticaldirection of the lower arm LA with respect to the sub frame SF.Specifically, in accordance with a swing of the lower arm LA, the firstcoupling part 41 turns relative to the second coupling part 42. Themeasuring unit 43 measures a relative turn amount of the first couplingpart 41 as a displacement amount in the vertical direction of the lowerarm LA. The measuring unit 43 has, as an example, a magnet and a halldevice and detects a change in a magnetic flux accompanying turn of thefirst coupling part 41 by the hall device. The measuring unit 43 maymeasure the relative turn amount of the first coupling part 41 by aconfiguration in which a light emission diode and a photo transistor arecombined. The vehicle height sensor 40 sequentially provides an outputvalue of the measuring unit 43 as detection information to the displaycontrol device 100.

As illustrated in FIG. 1, the display control device 100 is anelectronic control unit configured mainly by a computer having aprocessor 61, a RAM 62, a memory device 63, and an input/outputinterface. The processor 61 has a configuration including at least oneof a CPU (Central Processing Unit), a GPU (Graphics Processing Unit),and an FPGA (Field-Programmable Gate Array). The processor 61 mayinclude a dedicated processor specialized in learning of AI (ArtificialIntelligence) and inference. In the memory device 63, various programsexecuted by the processor 61 are stored. Concretely, in the memorydevice 63, an orientation detection program, a display control program,and the like are stored.

The orientation detection program is a program calculating theorientation angle of a vehicle and, as illustrated in FIGS. 3 and 4, aprogram capable of computing a road gradient θ of a road on which thevehicle is travelling, a pitch angle occurring in the vehicle, and avehicle gradient ϕ with respect to a horizontal reference plane HRP. Thehorizontal reference plane HRP is a virtual plane perpendicularlycrossing the gravity direction. As illustrated in FIG. 3, when thevehicle is travelling on a flat road which is along the horizontalreference plane HRP and has no tilt, the road gradient θ and the vehiclegradient ϕ are the same and substantially zero. In addition, in the casewhere the vehicle is placed on a flat road and both acceleration andbrake force in the front-rear direction do not work, the pitch angle issubstantially zero. On the other hand, as illustrated in FIG. 4, when avehicle travels on a sloping road inclined with respect to thehorizontal reference plane HRP, the vehicle gradient ϕ becomes a valuedifferent from the road gradient θ. Concretely, a value obtained byadding the pitch angle occurring in the vehicle to the road gradient θbecomes the vehicle gradient ϕ.

The display control program is a program controlling display of thevirtual image Vi and, as illustrated in FIGS. 5 and 6, a programrealizing augmented reality (hereinbelow, “AR”) display performed bysuperimposing the virtual image Vi on a superimposition object in aforeground. As an example, the display control program superimposes thevirtual image Vi indicating the range of a vehicle line during travelbetween right and left compartment lines in the foreground. The shape ofthe road surface visually recognized by the driver through theprojection area PA in the case where the vehicle travels on a flat road(refer to FIG. 3) and that in the case where the vehicle travels on asloping road (refer to FIG. 4) are different. Consequently, whencorrection in the sloping road is not executed, a virtual image Vix(refer to FIG. 4) deviated from the superposition object may bedisplayed. By using a computation result of the orientation detectionprogram, the display control program properly controls an imageformation position and shape of the virtual image Vi in accordance withthe road gradient θ, a change in the orientation of the vehicle, and thelike.

As illustrated in FIG. 1, the display control device 100 has functionblocks such as an information processing unit 71, a gradient calculationunit 72, a state estimation unit 73, a correlation correction unit 74,and an orientation computation unit 75 by execution of an orientationdetection program by the processing unit 61. In addition, the displaycontrol device 100 has function blocks such as a correction valuecomputation unit 76 and a display control unit 77 by execution of adisplay control program by the processing unit 61.

The information processing unit 71 obtains an output value of thevehicle height sensor 40 as detection information indicating a relativedistance between the sub frame SF and the lower arm LA (refer to FIG.2). In addition, the information processing unit 71 detects a no-loadstate in which a load causing a displacement in the vertical directionin a vehicle does not work on the basis of state information obtainedfrom the state estimation unit 73. The information processing unit 71sets an output value of the vehicle height sensor 40 in the no-loadstate as an initial value indicating the state where the pitch angle iszero.

The gradient calculation unit 72 obtains three-dimensional map data fromthe three-dimensional map data from the three-dimensional map DB 22 onthe basis of the position information of the vehicle obtained from theself-vehicle position detection device 21. The gradient calculation unit72 calculates the road gradient θ (refer to FIG. 4) of the road on whichthe vehicle travels by using the obtained three-dimensional map data.The road gradient θ is gradient information indicating a longitudinalgradient of a road, which is a positive value on an up-hill slope (referto FIG. 4) and a negative value in a down-hill slope.

As an example, as illustrated in FIG. 7, the gradient calculation unit72 specifies each of coordinates (refer to (X, Y, Z) of FIG. 7)indicating latitude, longitude, and altitude of two points P1 and P2specifying a sloping road from information of a point group included inthe three-dimensional map data. The gradient calculation unit 72 obtainsthe road gradient θ of the sloping road by geometric calculation usingthe coordinates of the two points P1 and P2.

The gradient calculation unit 72 illustrated in FIG. 1 may obtainvehicle speed information from the state estimation unit 73 and correctthe position information of the vehicle. Specifically, in positioninformation obtained from the self-vehicle position detection device 21,almost predetermined delay time (100 to 200 milliseconds) occurs.Therefore, the gradient calculation unit 72 can specify the presentposition of the vehicle with high precision by correcting a distanceamount of the vehicle moved in delay time from the position informationon the basis of the vehicle speed information on a map.

The state estimation unit 73 estimates the state of the vehicle on thebasis of various information obtained from the vehicle state sensor 26and the occupant sensor 27. The state estimation unit 73 obtains adetection result of an occupant by the occupant sensor 27 and estimatesthe weight of the vehicle and gravity position on the basis of thenumber of occupants detected and seating positions. In estimation of theweight and the gravity position, the weight value of each of theoccupants is substituted by a preliminarily designated average value. Inaddition, the state estimation unit 73 determines whether the vehicle isin a no-load state or not by combining vehicle speed information,steering information, acceleration information, accelerator positioninformation, and brake pedal force information. The state informationindicating the no-load state of the vehicle is provided to theinformation processing unit 71 and used for setting an initial value.

The correlation correction unit 74 executes a process of correctingcorrelation (hereinbelow, “correlation correcting process”) between anoutput value of the vehicle height sensor 40 and the pitch angle of thevehicle as detection information. The correlation correction unit 74obtains the state information of the vehicle estimated by the stateestimation unit 73 and obtains a tilt model corresponding to the presentweight and gravity position from the model storage unit 24. The tiltmodel obtained is a function showing correlation between the outputvalue of the vehicle height sensor 40 and the pitch angle on the flatroad (refer to FIG. 3).

The correlation correction unit 74 performs calibration of the tiltmodel in accordance with the state of the vehicle. Concretely, thecorrelation correction unit 74 obtains the road gradient θ calculated bythe gradient calculation unit 72. The correlation correction unit 74changes the tilt of the function (refer to the solid line in FIG. 8) asa reference in assumption of a flat road in accordance withpositive/negative and absolute values of the road gradient θ (refer tothe broken lines in FIG. 8). The correlation correction unit 74 executesthe above-described process as the correlation correcting process.

The correlation correction unit 74 may perform, as the correlationcorrecting process, a process of properly reading a tilt modelcorresponding to both the weight and gravity position and the roadgradient θ from the model storage unit 24. Alternatively, thecorrelation correction unit 74 may execute, as the above-describedcorrelation correcting process, a process of correcting a tilt model asa reference on the basis of both the weight and the gravity position andthe road gradient θ.

The orientation computation unit 75 repeatedly executes the orientationdetecting process (refer to FIG. 9). Concretely, the orientationcomputation unit 75 obtains an output value of the vehicle height sensor40 from the information processing unit 71 (refer to S11 in FIG. 9) andobtains a corrected tilt model (refer to FIG. 8) from the correlationcorrection unit 74 (refer to S12 in FIG. 9). The orientation computationunit 75 calculates a pitch angle occurring in the vehicle (refer to S13in FIG. 9) by a process of applying the output value of the vehicleheight sensor 40 to the tilt model (refer to the chain-line arrows inFIG. 8). The orientation computation unit 75 may execute the process ofobtaining a tilt model prior to the process of obtaining an outputvalue.

A correction value computation unit 76 repeatedly executes a correctionvalue computing process (refer to FIG. 10). The correction valuecomputing process is a process of generating correction information forcorrecting a deviation or the like of the projection position of adisplay light image accompanying a change in the pitch angle. Thecorrection value computation unit 76 obtains the pitch angle (refer toS21 in FIG. 10) from the orientation computation unit 75 and obtains theroad gradient θ (refer to FIG. 7) as gradient information from thegradient calculation unit 72 (refer to S22 in FIG. 10). The correctionvalue computation unit 76 calculates the vehicle gradient ϕ (refer toS23 in FIG. 10) by a process of adding the pitch angle to the roadgradient θ. Further, the correction value computation unit 76 computescorrection information for correcting the image formation position andthe shape of the virtual image Vi on the basis of the calculated vehiclegradient ϕ (refer to S24 in FIG. 10). The correction value computationunit 76 may execute the process of obtaining the road gradient θ priorto the process of obtaining the pitch angle.

The display control unit 77 generates video image data of the displaylight image projected by the projector 11 and sequentially outputs ittoward the optical unit 10. In the optical unit 10, the light of thedisplay light image based on the video image data is projected to theprojection area PA and formed as the virtual image Vi. The displaycontrol unit 77 specifies a relative position of a superimpositionobject on which the virtual image Vi is superimposed on the basis of thethree-dimensional map data, recognition information of an externalsensor of a camera or the like mounted in the vehicle, and the like. Thedisplay control unit 77 sets a projection position to which the light ofthe display light image is projected in the projection area PA bygeometric computation on the basis of the relations of the relativeposition of the superimposition object obtained and the positions of theeyellipse of the driver and the projection area PA. The display controlunit 77 sets, as a reference position, the projection position of thedisplay light image in the case where the road gradient θ issubstantially zero and no change occurs in the orientation of thevehicle.

The display control unit 77 generates video image data in which adeviation in the projection position of the display light imageaccompanying a change in the road gradient θ and the pitch angle iscorrected in advance. Specifically, the display control unit 77calculates a correction amount from the reference position of theprojection position of the display light image accompanying a change inthe road gradient θ and the pitch angle on the basis of the correctioninformation obtained from the correction value computation unit 76. Thedisplay control unit 77 sets a drawing position and the shape of anoriginal image which becomes the virtual image Vi so that the displaylight image is projected in the corrected projection position in whichthe correction amount is reflected in each of the frames constructingthe video image data and displays the virtual image by the optical unit10. By such a process, the virtual image Vi can be correctlysuperimposed on the superimposition object such as the road surface alsoin a vehicle which is climbing on a sloping road (refer to FIG. 6).

As described above, the correlation between the output value of thevehicle height sensor 40 and the pitch angle may indicate asubstantially unique change in accordance with the magnitude of the roadgradient θ. By paying attention to such a phenomenon, in the firstembodiment, based on gradient information grasped from three-dimensionalmap data, the function (tilt model) indicating the correlation betweenthe output value of the vehicle height sensor 40 and the pitch angle canbe corrected to a state adapted to the vehicle gradient ϕ of a road onwhich the vehicle is travelling. By the above, also during travel on asloping road with a gradient, the pitch angle computed becomesinsusceptible to the influence of the road gradient θ and can become avalue maintaining precision. Therefore, while avoiding complication ofthe configuration for orientation detection, decrease in detectionprecision of a pitch angle caused by the road gradient θ can besuppressed.

In addition, in the first embodiment, the vehicle gradient ϕ iscalculated by using the detected pitch angle, and the image formationposition and the shape of the virtual image Vi are corrected by usingcorrection information computed from the vehicle gradient ϕ. Asdescribed above, by using the pitch angle whose detection precision isassured for the process of making the virtual image Vi follow asuperimposition object in the foreground, the high-quality AR displayusing the virtual image Vi can be provided to the driver.

The display control device 100 of the first embodiment calculates thepitch angle of the vehicle by using the output value of the vehicleheight sensor 40. Such a vehicle height sensor 40 is widely spread as adetection configuration used for, for example, a system of adjusting theoptical axis of a headlight. Therefore, the display control device 100obtaining the pitch angle whose precision is assured from the outputvalue of the vehicle height sensor 40 by using a tilt model calibratedin accordance with the vehicle state can remarkably contribute toimprovement of realization of the virtual image display system 110performing AR display by using the virtual image Vi.

In the first embodiment, the vehicle height sensor 40 corresponds to a“sensor”, the information processing unit 71 corresponds to a “detectioninformation obtaining unit”, the gradient calculation unit 72corresponds to a “gradient information obtaining unit”, and the displaycontrol device 100 corresponds to an “orientation detection device”.

Second Embodiment

A second embodiment illustrated in FIGS. 11 to 13 is a modification ofthe first embodiment. A display control device 200 of the secondembodiment is connected to a front camera 23 in place of theself-vehicle position detection device 21 and the three-dimensional mapDB 22. Processes executed by the gradient calculation unit 72, thecorrection value computation unit 76, and the display control unit 77 inthe display control device 200 are different from those in the firstembodiment.

The front camera 23 is disposed near a back mirror in the compartment ofthe vehicle in a posture facing (forward) the travel direction of thevehicle. The imaging range of the front camera 23 is set, particularly,in a forward area in the surrounding of the vehicle. The front camera 23continuously shoots the forward area and generates a series of images Piof the road surface and horizontal lines in the travel direction. Theimage Pi taken by the front camera 23 is used for control of, forexample, a pre-crash safety system, a lane keeping assist, and the like.

The gradient calculation unit 72 can obtain, in addition to informationindicating an estimation value of the weight of the vehicle, acceleratorposition information, acceleration information, and the like output fromthe vehicle state sensor 26 from the state estimation unit 73. Thegradient calculation unit 72 has the function of determining whether ornot the surface of the road on which the vehicle is travelling is asubstantially horizontal road which is along the horizontal referenceplane HRP. Concretely, the gradient calculation unit 72 determineswhether the vehicle is travelling on a horizontal road or not on thebasis of comparison between the accelerator position and theacceleration in the front-rear direction generated in the vehicle.

More specifically, the drive force of a vehicle can be estimated on thebasis of the accelerator position information. In addition, the weightof the vehicle is estimated by the state estimation unit 73 on the basisof the detection result of the occupant sensor 27. Therefore, theacceleration generated in the vehicle on the horizontal road isunconditionally derived from the accelerator position information.Consequently, in the case where actual acceleration indicated by theacceleration information is the same as or similar to the accelerationderived from the accelerator position information, the state estimationunit 73 can determine that the vehicle is travelling on a horizontalroad.

The gradient calculation unit 72 obtains gradient information indicatingthe road gradient θ of the road on which the vehicle travels on thebasis of the image Pi of the forward area taken by the front camera 23.In the case where the gradient in a road section (hereinbelow, “firstsection S1”) in which the vehicle is traveling and that in a forwardroad section (second section S2) are different (refer to FIG. 12), inthe image Pi, a compartment line CL2 in the second section S2 is bentwith respect to a compartment CL1 of the first section S1 (refer to FIG.13). The gradient calculation unit 72 computes a road gradient relativeto the first section S1 of the second section S2, in other words, achange amount θr of a longitudinal gradient from the interval between avirtual crossing point CP1 on extension of the two compartment lines CL1and a virtual crossing point CP2 on extension of the two compartmentlines CL2. As described above, a relative gradient of a road in thetravel direction can be computed on the basis of the image Pi.

The gradient calculation unit 72 repeats a cumulative process of addingor subtracting a change amount θr of the longitudinal gradientcalculated from the image Pi using the road gradient of a horizontalroad on which the vehicle is travelling as a reference and obtains theroad gradient θ of the road on which the vehicle is travelling. When itis determined that the first section S1 during travel is a horizontalroad, the gradient calculation unit 72 resets the road gradient θ tozero as a reference value. The road gradient θ based on the image Picalculated as described above is provided to the correlation correctionunit 74 and used for calibration of a tilt model.

The correction value computation unit 76 repeatedly executes thecorrection value computing process (refer to FIG. 10) to continuouslycompute the correction information for correcting the image formationposition and the shape of the virtual image Vi in accordance with thevehicle gradient ϕ (refer to FIG. 4). The correction value computationunit 76 sequentially provides the obtained correction information to theoptical unit 10, not to the display control unit 77.

The display control unit 77 generates video image data of a displaylight image and sequentially outputs it toward the optical unit 10. Tothe projector 11 of the optical unit 10, both the video image data andthe correction information is input. The projector 11 corrects thedrawing position and the shape of the original image in each of framesof the video image data on the basis of the correction information and,then, projects the corrected image to the projection area PA. By theabove operations, superimposition of the virtual image Vi to thesuperimposition object is correctly executed also in a vehicle travelingon a sloping road (refer to FIG. 6).

In the foregoing second embodiment, on the basis of the image Pi takenby the front camera 23, gradient information of a road on which thevehicle is travelling is obtained. Based on such gradient information aswell, the correlation between the output value of the vehicle heightsensor 40 and the pitch angle can be corrected to a state adapted to theroad gradient θ of a road on which the vehicle is travelling. Therefore,also in the second embodiment, while avoiding complication of theconfiguration used for orientation detection, decrease in the detectionprecision of the pitch angle caused by the road gradient θ can besuppressed.

In addition, in the second embodiment, the horizontal road determiningprocess is executed, and the value of the road gradient θ is reset tozero as a reference value during travel on a horizontal road. Therefore,even in a form of calculating the road gradient θ by using the image Pi,deterioration in precision of the road gradient θ caused by accumulationof errors in the change amount θr can be suppressed. As a result, thedetection precision of the pitch angle can be highly maintained. In thesecond embodiment, the front camera 23 corresponds to an “imaging unit”,and the display control device 200 corresponds to an “orientationdetection device”.

Third Embodiment

A third embodiment illustrated in FIG. 14 is another modification of thefirst embodiment. A vehicle in which a display control device 300according to the third embodiment is mounted has an automatic drivingfunction capable of performing driving operation of the vehicle onbehalf of the driver. The automatic driving function is realized mainlyby an automatic driving ECU 25. The automatic driving ECU 25 is one of aplurality of electronic control units mounted in the vehicle anddirectly or indirectly electric-connected to a configuration such as thedisplay control device 300.

The automatic driving ECU 25 has a function of recognizing aself-vehicle position on the basis of position information andthree-dimensional map data, a function of recognizing the periphery ofthe vehicle from detection information of the front camera 23 and thelike, a function of drawing up an action plan of the vehicle, a functionof controlling vehicle behavior on the basis of the action plan, and thelike. The automatic driving ECU 25 makes the vehicle autonomously travelby obtaining a control right of the driving operation from the driver(automatic driving mode). On the other hand, in a state of manualdriving (manual driving mode) in which the driver has the control rightof the driving operation, the automatic driving ECU 25 stops theautomatic driving function.

The state estimation unit 73 is connected to the automatic driving ECU25 in addition to the vehicle state sensor 26 and the occupant sensor27. The state estimation unit 73 obtains status information indicativeof the operation state of the automatic driving function from theautomatic driving ECU 25. The state estimation unit 73 sequentiallyoutputs the status information obtained from the automatic driving ECU25 to the gradient calculation unit 72.

The gradient calculation unit 72 is connected to the front camera 23 inaddition to the self-vehicle position detection device 21 and thethree-dimensional map DB 22. The gradient calculation unit 72 has acomputation function substantially the same as that of the firstembodiment of calculating the road gradient θ on the basis of theposition information and the three-dimensional map data (refer to FIG.7) and a computation function substantially the same as that of thesecond embodiment of calculating the road gradient θ from the image Pitaken by the front camera 23 (refer to FIG. 13). The gradientcalculation unit 72 switches the method of calculating the road gradientθ on the basis of the status information of the automatic driving.

Concretely, in the automatic driving mode in which the automatic drivingfunction makes the vehicle autonomously travel, the gradient calculationunit 72 calculates the road gradient θ on the basis of the positioninformation and the three-dimensional map data. On the other hand, inthe manual driving mode in which the automatic driving function isstopped, the gradient calculation unit 72 calculates the road gradient θon the basis of the image Pi (refer to FIG. 13). The road gradient θobtained by one of the calculating methods is provided to thecorrelation correction unit 74 and used for correction of thecorrelation function (refer to FIG. 7) as a tilt model.

Like the third embodiment described above, the gradient calculation unit72 may switch the method for obtaining gradient information among aplurality of methods. Even when gradient information obtained bydifferent calculating methods is used, the correlation between theoutput value of the vehicle height sensor 40 and the pitch angle can becorrected to a state adapted to the road gradient θ of a road on whichthe vehicle is traveling. Therefore, also in the third embodiment, whileavoiding complication of the configuration used for orientationdetection, decrease in detection precision of the pitch angle caused bythe road gradient θ can be suppressed.

In addition, the three-dimensional map data is prepared preferentiallyfor an area in which autonomous travel by the automatic driving functioncan be performed. Therefore, the presence/absence of three-dimensionalmap data can be closely related to whether it is in a range in which theautonomous travel by the automatic driving function can be performed. Bysuch background, the gradient calculation unit 72 switches from thecalculating method using three-dimensional map data to a calculatingmethod which does not depend on three-dimensional map data inassociation with the operation stop of the automatic driving function.By the above, the gradient calculation unit 72 can smoothly complete theswitching of the calculating method before it becomes impossible toobtain three-dimensional map data. Therefore, also in the case where thevehicle moves from an area where three-dimensional map data is preparedto an area in which the data is not prepared, computation of the pitchangle in which precision is assured can be continued. As a result, thestate where the virtual image Vi is correctly superimposed on thesuperimposition object can also be maintained with high reliability. Inthe third embodiment, the display control device 300 corresponds to an“orientation detection device”.

Fourth Embodiment

A fourth embodiment illustrated in FIG. 15 is further anothermodification of the first embodiment. A virtual image display device 410according to the fourth embodiment has a configuration that a displaycontrol device and a display are integrated, and has the optical unit 10and a display control circuit 400. The display control circuit 400 is anelectric configuration corresponding to a display control device and hasa plurality of function blocks (71 to 77).

The gradient calculation unit 72 of the display control circuit 400obtains, in a manner similar to the second embodiment, informationindicative of an estimation value of the weight of a vehicle and, inaddition, the accelerator position information, the accelerationinformation, and the like output from the vehicle state sensor 26 fromthe state estimation unit 73. The gradient calculation unit 72 has, inaddition to the computation function (refer to FIG. 7) substantially thesame as that of the first embodiment of calculating the road gradient θfrom the position information and three-dimensional map data, acomputation function of calculating the road gradient θ on the basis ofcomparison between accelerator position and acceleration.

As described above, the acceleration generated in a vehicle whichtravels on a horizontal road can be unconditionally derived fromaccelerator position information. Therefore, the difference betweenactual acceleration (hereinbelow, “measurement acceleration”) indicatedby acceleration information and acceleration (hereinbelow, “estimatedacceleration”) derived from the accelerator position informationincreases/decreases depending on the magnitude of slope climb resistanceacting on a vehicle, that is, the magnitude of the road gradient θ. Bythe above, a three-dimensional computation map of calculating the roadgradient θ from the accelerator position information and theacceleration information can be specified in advance. The gradientcalculation unit 72 can calculate the road gradient θ by application ofthe accelerator position information and the acceleration information tothe computation map.

In the case where three-dimensional map data can be obtained from thethree-dimensional map DB 22, the gradient calculation unit 72 calculatesthe road gradient θ on the basis of the position information and thethree-dimensional map data. On the other hand, in the case wherethree-dimensional map data of a road on which a vehicle travels cannotbe obtained in an area in which three-dimensional map data is not ready,the gradient calculation unit 72 calculates the road gradient θ on thebasis of comparison between accelerator position information andacceleration information. The road gradient θ obtained by any one of thecalculating methods is provided to the correlation correction unit 74and used for correction of the correlation function (refer to FIG. 7).

In the fourth embodiment described above, based on comparison betweenthe accelerator position and the acceleration in the front-reardirection, gradient information of a road on which the vehicle istravelling is obtained. Also based on such gradient information, thecorrelation between the output value of the vehicle height sensor 40 andthe pitch angle can be corrected to a state adapted to the road gradientθ of a road on which the vehicle is travelling. Therefore, also in thefourth embodiment, while avoiding complication of the configuration usedfor orientation detection, decrease in the detection precision of thepitch angle caused by the road gradient θ can be suppressed.

In addition, the AP sensor detecting the accelerator position, theacceleration sensor detecting acceleration in the front-rear direction,and the like are detection configurations already mounted in a generalvehicle. Therefore, in employment of the calculating method of thepresent disclosure of estimating the road gradient θ by using suchdetection configurations, together with the configuration of detecting adisplacement in the vertical direction only by a single vehicle heightsensor 40, addition of a configuration for orientation detection can besuppressed to minimum. In the fourth embodiment, the virtual imagedisplay device 410 corresponds to the “orientation detection device”.

Fifth Embodiment

A fifth embodiment illustrated in FIG. 16 is further anothermodification of the first embodiment. The function of an orientationdetection device in the fifth embodiment is realized by an optical axiscontrol device 500. The optical axis control device 500 is connected toa lighting unit 510 and adjusts the position of an optical axis OA of aheadlight in the vertical direction.

The optical axis control device 500 has, in addition to a plurality offunction blocks (71 to 75) similar to those in the first embodiment, anoptical axis control unit 577. In the fifth embodiment, the method ofcalculating the road gradient θ executed by the gradient calculationunit 72 is different from that in the first embodiment. Hereinafter, thedetails of processes executed by the gradient calculation unit 72 andthe optical axis control unit 577 will be described in order.

The gradient calculation unit 72 obtains accelerator positioninformation and acceleration information from the vehicle state sensor26. In a manner similar to the fourth embodiment, the gradientcalculation unit 72 obtains an estimation value of vehicle weightestimated by the state estimation unit 73 and calculates the roadgradient θ on the basis of comparison between the accelerator positionand the acceleration. The road gradient θ calculated by the gradientcalculation unit 72 is provided to the correlation correction unit 74and used for calibration of a tilt model.

The optical axis control unit 577 adjusts the optical axis OA of theheadlight to a proper position in cooperation with the optical axisadjustment mechanism 511 provided for the lighting unit 510. In theorientation computation unit 75, by fitting an output value of thevehicle height sensor 40 to the tilt model calibrated by the correlationcorrection unit 74, a pitch angle is calculated. The optical axiscontrol unit 577 corrects a deviation of the optical axis OAaccompanying a change in the orientation of the vehicle by using thepitch angle calculated by the orientation computation unit 75. By theabove, also in a vehicle which travels, particularly, up or down on asloping road, the optical axis OA is adjusted to a position where theroad surface of the sloping road can be irradiated correctly.

The fifth embodiment described above also produces effects similar tothose of the first embodiment, and the correlation between the outputvalue of the vehicle height sensor 40 and the pitch angle can becorrected to a state adapted to the road gradient θ. Therefore, whileavoiding complication of the configuration used for orientationdetection, decrease in detection precision of the pitch angle caused bythe road gradient θ can be suppressed.

In addition, in the fifth embodiment, by the process of applying theoutput value of the vehicle height sensor 40 to the tilt modelcalibrated in accordance with the road gradient θ, a pitch angle of thevehicle is obtained, and the position of the optical axis OA is adjustedon the basis of the pitch angle. The position control of the opticalaxis OA can continuously properly maintain the irradiation range of theheadlight more than a conventional technique in which the optical axisOA is adjusted by using an output value of the vehicle height sensor 40without considering the road gradient θ. In the fifth embodiment, theoptical axis adjustment mechanism 511 corresponds to an “optical axisadjustment unit”, and the optical axis control device 500 corresponds toan “orientation detection device”.

Other Embodiments

Although the plurality of embodiments of the present disclosure havebeen described above, the present disclosure is not interpreted by beinglimited to the foregoing embodiments but can be applied to variousembodiments and combinations in a range which does not depart from thegist of the present disclosure.

In a first modification of the embodiment, an acceleration sensor fordetecting acceleration in the vertical direction is used as a sensordetecting a displacement in the vertical direction occurring in avehicle. The acceleration sensor measures relative acceleration betweenthe body and the suspension arm. An information processing unit in thefirst modification obtains a displacement amount in the verticaldirection by computation of time-integrating the relative accelerationdetected by the acceleration sensor twice. The information processingunit can obtain detection information corresponding to an output valueof the vehicle height sensor by a process of integrating a displacementamount.

In a second modification of the third embodiment, the gradientcalculation unit switches the method of calculating the road gradient θon the basis of whether three-dimensional map data can be obtained ornot. In an area where the three-dimensional map data is prepared, thegradient calculation unit calculates the road gradient θ on the basis ofthe three-dimensional map data and position information. On the otherhand, in an area where the three-dimensional map data is not ready andthree-dimensional map data of a road on which the vehicle travels cannotbe obtained, the gradient calculation unit obtains the road gradient θon the basis of the image Pi taken by the front camera 23.

In a third modification of the third embodiment, the gradientcalculation unit has three computation functions of calculating the roadgradient θ. Specifically, in the case where the automatic drivingfunction operates, the gradient calculation unit calculates the roadgradient θ on the basis of three-dimensional map data. When theautomatic driving function is stopped, the gradient calculation unit 72calculates the road gradient θ on the basis of the image Pi. Further, inthe case where it is difficult to extract the compartment line CL fromthe image Pi, the gradient calculation unit calculates the road gradientθ on the basis of comparison between accelerator position andacceleration.

In a fourth modification of the fourth embodiment, the display controldevice is connected to the automatic driving ECU. In a manner similar tothe third embodiment, in the case where the automatic driving functionmakes the vehicle autonomously travel, the gradient calculation unit ofthe fourth modification calculates the road gradient θ on the basis ofposition information and three-dimensional map data. On the other hand,in the case where the automatic driving function stops, the gradientcalculation unit calculates the road gradient θ on the basis ofcomparison between accelerator position and acceleration.

The gradient calculation unit of the embodiment obtains a tilt model ofa vehicle from the model storage unit connected to the display controldevice. However, the configuration of storing a tilt model is notlimited to an external model storage unit but may be a memory device inthe display control device.

In the first to fourth embodiments, by the process of correcting anoriginal image in each of frames of video image data, display in whichthe virtual image Vi is superimposed on the superimposition object ismaintained. However, when the optical unit is provided with anadjustment mechanism of adjusting the orientation of the reflectiveoptical system, by a mechanical control of operating the adjustmentmechanism on the basis of correction information, the superimpositionstate of the virtual image Vi may be maintained.

The optical axis control device of the fifth embodiment is providedseparately from the lighting unit. However, a control circuitcorresponding to the optical axis control device may be providedintegrally with the lighting unit. Further, the optical axis adjustmentmechanism may be a configuration of mechanically changing theorientation of the headlight or a configuration of electricallycontrolling a light-on state of a plurality of light emission diodes.

The process for orientation detection described above may be executed bya configuration different from the display control device, the displaycontrol circuit, and the like. For example, a combination meter, anavigation device, or the like may obtain the function of theorientation detection device by executing the orientation detectionprogram by a control circuit. In such a manner, the function of theorientation detection device may be a function of one of function partsmounted in a vehicle. Further, the control circuit of the automaticdriving ECU may function as the process unit of executing computationbased on the orientation detection program. Alternatively, a pluralityof control circuits of the display control device, the display device,the automatic driving ECU, and the like may dispersedly process thecomputation for orientation detection.

Various non-transitory tangible storage media such as a flash memory anda hard disk can be employed in the memory device as a configuration ofstoring the orientation detection program. In addition, a storage mediumstoring the orientation detection program is not limited to the storagemedium provided for the electronic control unit mounted in a vehicle butmay be an optical disk, a hard disk drive of a general computer, or thelike as a copy source to the storage medium.

It is noted that a flowchart or the processing of the flowchart in thepresent disclosure includes sections (also referred to as steps), eachof which is represented, for instance, as S101. Further, each sectioncan be divided into several sub-sections while several sections can becombined into a single section. Furthermore, each of thus configuredsections can be also referred to as a circuit, device, module, or means.

Each or any combination of sections explained in the above can beachieved as (i) a software section in combination with a hardware unit(e.g., computer) or (ii) a hardware section, including or not includinga function of a related apparatus; furthermore, the hardware section(e.g., integrated circuit, hard-wired logic circuit) may be constructedinside of a microcomputer.

What is claimed is:
 1. An orientation detection device for detectingorientation of a vehicle, comprising: a detection information obtainingunit that obtains a detection information of a sensor, which detects adisplacement in a vertical direction occurring in the vehicle; anorientation computation unit that computes a pitch angle of the vehicleon the basis of the detection information; a gradient informationobtaining unit that obtains a gradient information indicating a gradientof a road on which the vehicle travels; and a correlation correctionunit that corrects a correlation between the detection information usedin computation of the orientation computation unit and the pitch angleon the basis of the gradient information.
 2. The orientation detectiondevice according to claim 1, wherein the gradient information obtainingunit obtains the gradient information on the basis of three-dimensionalmap data.
 3. The orientation detection device according to claim 1,wherein the gradient information obtaining unit obtains the gradientinformation on the basis of an image of surrounding of the vehicle takenby an imaging unit.
 4. The orientation detection device according toclaim 2, wherein the gradient information obtaining unit obtains thegradient information on the basis of an image of surrounding of thevehicle taken by an imaging unit, in a case where the three-dimensionalmap data is not obtained.
 5. The orientation detection device accordingto claim 2, wherein the vehicle has an automatic driving function, thegradient information obtaining unit obtains the gradient information onthe basis of the three-dimensional map data in response to the automaticdriving function being in operation to make the vehicle travel, and thegradient information obtaining unit obtains the gradient information onthe basis of an image of surrounding of the vehicle taken by an imagingunit in response to the automatic driving function being not inoperation.
 6. The orientation detection device according to claim 3,wherein the gradient information obtaining unit determines whether thevehicle travels on a horizontal road on the basis of comparison betweenan accelerator position of the vehicle which is traveling and anacceleration in the front-rear direction generated in the vehicle, andcomputes a gradient of a road in the travel direction using, as areference, the road gradient of the horizontal road on which the vehicletravels on the basis of the image.
 7. The orientation detection deviceaccording to claim 1, wherein the gradient information obtaining unitobtains the gradient information on the basis of comparison between anaccelerator position of the vehicle during travel and an acceleration inthe front-rear direction generated in the vehicle.
 8. The orientationdetection device according to claim 2, wherein in a case where thethree-dimensional map data regarding the road on which the vehicletravels cannot be obtained, the gradient information obtaining unitobtains the gradient information on the basis of comparison between anaccelerator position of the vehicle during travel and an acceleration inthe front-rear direction generated in the vehicle.
 9. The orientationdetection device according to claim 2, wherein the vehicle has anautomatic driving function, the gradient information obtaining unitobtains the gradient information on the basis of the three-dimensionalmap data in response to the automatic driving function being inoperation to make the vehicle travel, and the gradient informationobtaining unit obtains the gradient information on the basis ofcomparison between an accelerator position of the vehicle during traveland acceleration in the front-rear direction generated in the vehicle inresponse to the automatic driving function being not in operation. 10.The orientation detection device according to claim 1, which is to beconnected to an optical unit projecting a display light image to aprojection area designated in the vehicle and displaying a virtual imageof the display light image so that the virtual image is visible by anoccupant of the vehicle, the orientation detection device furthercomprising: a correction value computation unit that generates acorrection information for correcting a deviation of a projectionposition of the display light image in accordance with a change in thepitch angle by using the pitch angle calculated by the orientationcomputation unit.
 11. The orientation detection device according toclaim 10, further comprising a display control unit that generates avideo image data obtained by preliminarily correcting a deviation of aprojection position of the display light image in accordance with achange in the pitch angle by using the correction information anddisplays the video image data as a virtual image by the optical unit.12. The orientation detection device according to claim 1, furthercomprising: an optical unit that projects a display light image to aprojection area designated in the vehicle and displays a virtual imageof the display light image so that the virtual image is visuallyrecognized by an occupant of the vehicle; and a correction valuecomputation unit that generates a correction information for correctinga deviation of a projection position of the display light image inaccordance with a change in the pitch angle by using the pitch anglecalculated by the orientation computation unit.
 13. The orientationdetection device according to claim 1, which is to be connected to alighting unit that has an optical axis adjusting unit adjusting anoptical axis of a headlight of the vehicle, the orientation detectiondevice further comprising an optical axis control unit that corrects adeviation of the optical axis in accordance with an orientation changeof the vehicle by using the pitch angle calculated by the orientationcomputation unit.
 14. The orientation detection device according toclaim 1, wherein the detection information obtaining unit obtains, asthe detection information, at least one of a relative distance between abody of the vehicle and a suspension arm suspended in the body and arelative acceleration between the body and the suspension arm.
 15. Anon-transitory computer readable medium storing a computer programproduct comprising instructions for detecting orientation of a vehicle,the instructions being configured to, when executed by a processor,cause the processor to: obtain a detection information of a sensor,which detects a displacement in the vertical direction occurring in thevehicle; compute a pitch angle of the vehicle on the basis of thedetection information; obtain a gradient information indicating agradient of a road on which the vehicle travels; and corrects acorrelation between the detection information used in computation andthe pitch angle on the basis of the gradient information.
 16. Anorientation detection device for detecting orientation of a vehicle,comprising a processor configured to: obtain a detection information ofa sensor, which detects a displacement in a vertical direction occurringin the vehicle; compute a pitch angle of the vehicle on the basis of thedetection information; obtain a gradient information indicating agradient of a road on which the vehicle travels; and correct acorrelation between the detection information used in computation andthe pitch angle on the basis of the gradient information.